Stimulation of phospholipase D activity by phorbol esters in cultured astrocytes.
The phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) was found to stimulate phospholipase D activity in cultured primary astrocytes. Both the hydrolysis and the transphosphatidylation reaction catalyzed by phospholipase D were studied in cells labeled with [3H]glycerol. Phosphatidic acid (PA) synthesis was increased after addition of 100 nM TPA. When ethanol was present in the cell culture medium, phosphatidylethanol (Peth), a product of phospholipase D-catalyzed transphosphatidylation, was formed. The half-maximum effective concentrations (EC50) of TPA were 25 nM for PA increase as well as for Peth formation. The formation of Peth in ethanol-treated cells was accompanied by an inhibition of the TPA-induced increase in labeled PA. Increasing ethanol concentrations led to an increase in [3H]Peth and a decrease in [3H]PA. A protein kinase C inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7), inhibited both the synthesis of PA and the formation of Peth observed after TPA addition to the astrocytes. Dioctanoyl-glycerol (100 microM) stimulated the formation of Peth in the presence of ethanol. In addition to the induction of Peth formation in astrocytes, TPA induced Peth formation in ethanol-treated neurons. The present results indicate that phospholipase D activity is stimulated by TPA in cultured primary brain cells. Modulation of phospholipase D activity by protein kinase C is a mechanism that may be important in signal transduction cascades.
Gustavsson
L
L
Department of Psychiatry and Neurochemistry, University of Lund, Sweden.
Hansson
E
E
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D001253:Astrocytes / Q000201:enzymology*; D001696:Biomechanical Phenomena; D002478:Cells, Cultured; D004075:Diglycerides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D020404:Glycerophospholipids; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology; D010712:Phosphatidic Acids / Q000096:biosynthesis; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D011919:Rats, Inbred Strains; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000378:metabolism*
D004075:Diglycerides; D020404:Glycerophospholipids; D007546:Isoquinolines; D010712:Phosphatidic Acids; D010879:Piperazines; C051521:phosphatidylethanol; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate